Bimolecular Formation of Radicals by Hydrogen Transfer, 10. On the Mechanism of Quinone Dehydrogenations

Autor:	Christoph Rüchardt, Christoph Höfler
Rok vydání:	2006
Předmět:	Xanthene Hydride Radical Organic Chemistry General Chemistry Photochemistry Quinone Nitrosobenzene chemistry.chemical_compound chemistry Kinetic isotope effect Dehydrogenation Physical and Theoretical Chemistry Solvent effects
Zdroj:	Liebigs Annalen. 1996:183-188
ISSN:	1099-0690 0947-3440
DOI:	10.1002/jlac.199619960206
Popis:	The mechanistic alternatives in the literature for quinone dehydrogenations of hydroaromatic to aromatic hydrocarbons are reviewed. In a kinetic study of the reaction of DDQ 16 with 9,10-dihydroanthracene (13) or xanthene (17) small solvent effects and small rate differences between 13 and 17 (Table 1) but large kinetic isotope effects kH/kD were observed. In addition, intermediate 9-hydroanthryl radical 20b and 9-xanthyl radicals 19b were trapped by the addition of nitrosobenzene to the dehydrogenation reaction mixtures as shown by the ESR spectra of the spin adducts 22 and 23. These results are better explained by an initial H atom transfer step (retrodisproportionation, RD) than by direct hydride transfer (DHT). Possible consequences for biochemical hydrogen transfer processes are addressed briefly.
Databáze:	OpenAIRE
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